The present invention relates to electrostatic liquid spraying devices.
On the whole, such devices use a direct current high tension source in order to electrostatically charge the particles of the liquid spray. However, it is known from U.S. Pat. No. 1,958,406 to use a source of alternating potential in conjunction with an electrostatic spraying device but there is no explicit teaching as to the frequency employed. The general tenor of the disclosure implies that the frequency utilized is mains frequency, i.e. 60 Hz in the USA.
It is also known from UK Patent No 2128900 to provide a lever-operated spraying device in which an atomized spray is produced from a nozzle by squeezing the lever. This device includes a needle electrode positioned at or adjacent the nozzle and high voltage is applied to the needle electrode to ionize the spray emerging at the outlet of the nozzle. In one embodiment, the voltage generator is piezo-electric and the action of alternately squeezing and releasing the lever results in high voltage pulses of successive opposite polarity being applied to the electrode. During the squeezing action, spray is produced and the resulting droplets are charged by corona discharge from the electrode. During the release action, no spray will be produced but the high voltage at the needle may reverse in polarity to produce a corona discharge which may serve to eliminate or modify static when the device is used in certain applications.